#!/usr/bin/env bash

## 193. Valid Phone Numbers
## Given a text file file.txt that contains list of phone numbers (one per line), write a one liner bash script to print all valid phone numbers.
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## You may assume that a valid phone number must appear in one of the following two formats: (xxx) xxx-xxxx or xxx-xxx-xxxx. (x means a digit)
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## You may also assume each line in the text file must not contain leading or trailing white spaces.
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## Example:
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## Assume that file.txt has the following content:
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## 987-123-4567
## 123 456 7890
## (123) 456-7890
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## Your script should output the following valid phone numbers:
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## 987-123-4567
## (123) 456-7890
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## Read from the file file.txt and output all valid phone numbers to stdout.

## Using grep:

grep -P '^(\d{3}-|\(\d{3}\) )\d{3}-\d{4}$' file.txt

## Using sed:

sed -n -r '/^([0-9]{3}-|\([0-9]{3}\) )[0-9]{3}-[0-9]{4}$/p' file.txt

## Using awk:

awk '/^([0-9]{3}-|\([0-9]{3}\) )[0-9]{3}-[0-9]{4}$/' file.txt